As most of you have noted by now, the secret of our economical shelters resides in the repeatability provided to us by the geometries we use. In the RD's (rhombic dodecahedrons), all panels are parallelograms of the same size ( actually we use 2 sizes in our 'squashed' RD, one size for the walls and one size for both the roof and the underside panels). This allows for simple assembly jigs, a uniform press to inject all of these with urethane foam, uniform carrying carts, simplified loading of containers etc....
Moreover, since parallellograms can be made from rectangular building materials with no waste ( see this blog ), there is an added economy not present from regular construction where upwards of 20% of materials can end up in municipal dumps.
The other economies also derive from economy of scale. When hundreds of shelters are built using only a few identical parts, much less time is wasted in certification, inspection, training etc...Anf of course purchasing power is augmented to a great degree.